Graphics.Element middle position can be off by one pixel due to rounding

[parkermalenke]

Hello,

Just started playing around with Elm and am finding it very impressive! Keep up the great work.

I noticed that in certain cases attempting to position an element in the middle of another element results in a layout that is off by a single pixel. I believe this is because line 241 and 236 in the source javascript are using the bitwise or to round towards a single pixel instead of something like Math.round().

For a reproduction see this example which should draw a red rectangle with a single pixel border all the way around, but instead draws it with a 2px border at the top and left only.

import Graphics.Element (..)
import Color (red, blue)

main = spacer 99 19
  |> color red
  |> container 101 21 middle
  |> color blue

On an unrelated note, I noticed P, Z, and N seem to refer to different methods of setting an axis origin for positioning. This terminology is unfamiliar to me and I would be interested to know what it refers to.

[evancz]

Sorry this did not get attention til now! The Graphics.* modules now live in evancz/elm-graphics so I am trying to get stuff migrated over there. I'm hoping this will make it easier to get help on stuff like this!